I have used previous versions of Opera (up to 12) and there was always a pdf viewer installed automatically. I know version 26 is based on chrome but even Chrome downloads with a pdf viewer already installed.

I can't see opera:plugins in my version. There is Opera:get extensions and I can see 6 pdf extensions. Is open with Google drive viewer the preferred pdf extension for Opera?

I have typed opera://plugins in the address bar and Chrome PDF Viewer was there and enabled. After I did that on my laptop the pdf displayed although I can assure you they did not before I asked the question. I have just done it on the desktop and all I get is a blank screen just like the screenshot above.

This is the Opera details on my desktop. My laptop details are similar.
Version: 26.0.1656.60 - Opera is up to date
Update stream: Stable

You say the Chrome PDF viewer is there and enable, but are there any other PDF viewers there an enabled? Like the Mozilla/Firefox PDF viewer or another PDF viewer of some kind? If you have two enabled at the same time it can cause conflicts.

I have now got it working on the desktop by installing the 'pdf viewer' extension.

Chrome PDF viewer is still enabled in the plugins but as I said all I got a blank page so to view a pdf I need the two installed! It doesn't explain why I was eventually able to view a pdf on my laptop with only Chrome PDF viewer enabled.

Thanks for your reply.
I have now got it working on the desktop by installing the 'pdf viewer' extension.
Chrome PDF viewer is still enabled in the plugins but as I said all I got a blank page so to view a pdf I need the two installed! It doesn't explain why I was eventually able to view a pdf on my laptop with only Chrome PDF viewer enabled.
Anyway the main thing is that I can view pdf's using Opera!